When a plurality of ceramic wiring boards are manufactured with multi-piece-array, conventionally, a green sheet laminate body has been formed by laminating and press-bonding a plurality of green sheets where a conductor layer is formed on at least one of a front surface and a back surface of a green sheet laminate body, dividing grooves have been formed so as to have a predetermined depth along boundaries between individual wiring board regions of the laminate body by a blade (die), and a plurality of ceramic wiring boards have been simultaneously manufactured by cutting along the dividing grooves after firing the green sheet laminate body. However, there has been a problem in that the peripheral portions of the wiring board regions adjacent to the blade are deformed by the load of the blade when the blade is made to penetrate the soft green sheet laminate body.
In order to eliminate the deformation of the wiring board regions caused by the blade or jetty portions positioned in the vicinity of the open ends of the dividing grooves, there is proposed a method of manufacturing a ceramic board for division including dividing grooves, which have a substantially V-shaped cross-section and chamfered opening portions and do not include jettys in the vicinity of the open ends, by irradiating (scanning) the surface of a ceramic substrate, which is formed by firing the green sheet laminate body formed by laminating and press-bonding a plurality of green sheets, with a laser beam twice (for example, see PTL 1).
However, in the case of the dividing grooves that have a V-shaped cross-section and are formed by the irradiation of a laser beam as described above, a plurality of microcracks are irregularly generated toward the inside of the ceramic board from the vicinity of the deepest portions of the dividing grooves. As a result, the depth of the dividing groove becomes different from the set depth. For this reason, there has been a problem in that irregular chipping occurs from the vicinity of the dividing grooves in the following the firing step or a plating step subsequent to the firing step or cracking or breaking occurs on the individual wiring boards at the time of division in a dividing step to be further performed.